This disclosure generally relates to charging devices for batteries and, in particular, relates to charging devices for batteries used on airplanes.
Commercial airplanes utilize batteries of different technologies and corresponding battery chargers. Each charger employs a charging algorithm that corresponds to the particular battery technology and a power conversion architecture that suits the particular input power. In the past, in commercial aviation input power was always 115 V AC and constant 400 Hz frequency, while charger battery output was always between 24 and 32 V DC depending on the low-voltage battery technology used. For example, traditional chargers converting three-phase 115 V AC power to 28 V DC power were used with power conversion efficiencies in a range of 87 to 89%. Insignificant change in charger output voltage and a single standard for input power allowed for reusing legacy charger designs, slightly adjusting the charging logic to meet the particular battery technology.
Recent aerospace industry trends in reducing fuel burn, CO2 emissions and weight and improving overall efficiency have led to the introduction of new higher-voltage input power, which also became variable-frequency (VF) power. In addition, advances in battery technology and industry trends of using higher DC voltages for weight reduction prompted use of high-voltage batteries in many applications (76 V, 270 V, 540 V, etc.). These changes in the industry, coupled with large advances in power electronic devices (e.g., the commercial availability of wide-band gap SiC and GaN-based power switches), make it possible to revisit traditional battery charger designs with the purpose of designing a new universal charger architecture that is lighter and more efficient than traditional charger designs. In addition, for cost efficiency, this charger must be able to utilize any standard aircraft input voltage power (115 V AC, constant frequency or 230 V AC, variable frequency) while charging different batteries, including either traditional (24 and 32 V DC) or more recent high-voltage (200 and 320 V DC) batteries.
In view of the introduction of variable-frequency power, higher voltages, and different battery technologies in more recent airplane architectures, it would be advantageous to design a new universal battery charger that can operate in all common power system architectures and can charge all batteries, either traditional or high voltage.